The present invention relates to a rotating electric machine.
In some industrial vehicles such as forklift trucks including a rotating electric machine (e.g. a motor) as a power source for traction, the right drive wheel and the left drive wheel are driven by separate rotating electric machines. In such industrial vehicles, the right drive wheel is connected to the output shaft of the right rotating electric machine and the left drive wheel is connected to the output shaft of the left rotating electric machine, which enables a small-sized simplified structure that provides a desired drive force and a smaller turning radius. In each of the rotating electric machines, the output shaft that is provided on the side opposite to the output shaft connected to the drive wheels may be connected with a device such as a brake device. For this reason, left drive wheel, left rotating electric machine, left brake device, right brake device, right rotating electric machine, and right drive wheel are disposed serially in this order from the left drive wheel side toward the right drive wheel side. Thus, the length of a rotating electric machine in the axial direction thereof should preferably be as small as possible. Rotating electric machines used as a drive source for an industrial vehicle, for example, generate a large amount of heat. Therefore, the rotating electric machine for such industrial vehicle should preferably have a small, simplified cooling structure that utilizes air for cooling and more preferably should be equipped with a rotational speed detection gear having gear teeth for detecting a rotational speed of the rotating electric machine.
Japanese Unexamined Patent Application Publication No. 2013-110841 discloses a cooling structure for a brushless motor including a motor housing and a shaft (a motor shaft) supported at the opposite ends thereof through bearings in the motor housing, and a cooling fan that is provided outside the motor housing and sends air from one end toward the opposite end of the shaft along the axial direction thereof. The cooling structure further includes a cylindrical stator having a plurality of teeth provided in the circumferential direction thereof and a plurality of ventilation grooves is provided in an insulating member covering an end surface of the stator that is on the side opposite to the cooling fan at positions between any two adjacent teeth.
Japanese Unexamined Patent Application Publication No. 2001-238403 discloses an electric motor including a housing (an outer casing), a shaft (a rotating shaft) that is supported at the opposite ends thereof through a bearing in the housing. The housing has in peripheral walls thereof and at a position adjacent to one end of the shaft an air intake port and at a position adjacent to the other end of the shaft an air outlet port. A main plate is provided between a rotor and the other end of the shaft. The main plate has a conical surface extending to the air outlet port along the axial direction of the shaft and includes a plurality of fan blades on the conical surface. The shaft has at the other end thereof a rotating disc for a sensor (corresponding to the aforementioned rotational speed detection gear) that detects the rotating speed of the shaft. The housing has a speed sensor at a position of the housing facing the outer peripheral surface of the rotating disc for the sensor.
In the cooling structure for a brushless motor disclosed in Japanese Unexamined Patent Application Publication No. 2013-110841 wherein the cooling fan that is larger than the stator is mounted on the shaft outside the motor housing, the length of the motor in the axial direction thereof is increased by the dimension of the cooling fan. Furthermore, if a rotational speed detection gear is added to the cooling structure, the length of the motor in the axial direction is further increased.
As with the cooling structure of Japanese Unexamined Patent Application Publication No. 2013-110841, in the electric motor disclosed in Japanese Unexamined Patent Application Publication No. 2001-238403 wherein the conical main plate having fan blades is mounted on the shaft, the length of the electric motor in the axial direction is increased by the dimension of the main plate. Furthermore, the electric motor has the rotating disc for a sensor (corresponding to the above-described rotational speed detection gear) at the other end of the shaft and, therefore, the length of the electric motor in the axial direction is further increased.
The present invention has been made in view of the above problems and is directed to providing a rotating electric machine having a rotating member for air cooling and a rotation speed detection gear that can reduce the dimension of the rotating electric machine in the axial direction thereof and provides an appropriate path for cooling air.